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川中三叠系须家河组地层具有砂泥岩交互、大面积分布的特征,已发现的广安、合川、八角场等大型气田以及充西等含气构造。这套含气组合平面上分布于川中地区各个不同的构造区域,纵向上各储层段交互发育。它们成藏背景相似,但又相互独立,互不连通,表现为大面积成藏的地质特征。通过对须家河组成藏地质特征的深入分析认为,大面积成藏的主控因素包括:①平缓构造背景下,大型开放式浅水湖盆广泛发育煤系与砂岩的交互组合,是大面积成藏的基础;②优质储层的广泛分布,是大面积成藏的重要条件,主要受早印支期古构造、沉积微相以及裂缝的联合控制;③白垩纪末盆地的整体抬升,天然气发生膨胀排烃以及储层的分隔化对气藏的保存作用是大面积成藏的重要机制。
The Triassic Xujiahe Formation in the Central Sichuan Basin has the characteristics of sandstone-mudstone interaction and large area distribution, large-scale gas fields such as Guang’an, Hechuan and Bajiaochang discovered, and gas-bearing structures such as the western Sichuan. This set of gas-bearing planes are distributed in different tectonic areas in the central Sichuan Basin, and each reservoir section in the longitudinal direction develops interactively. They have similar reservoir forming backgrounds, but are independent of each other and are not connected to each other. They are characterized by the geological features of large-area accumulation. Based on the deep analysis of the geological characteristics of the Xujiahe Formation, the main controlling factors of the large-area accumulation include: (1) Under the gentle tectonic setting, the interaction between coal measures and sandstones is extensively developed in the large-scale open shallow lacustrine basin, (2) The extensive distribution of high-quality reservoirs is an important condition for large-area accumulation, which is mainly controlled by the Early Indosinian paleostructures, sedimentary microfacies and fractures. (3) The whole uplift of Cretaceous basins and the occurrence of natural gas Expansion and expulsion of hydrocarbons and reservoirs of the preservation of gas reservoirs is an important mechanism of large area accumulation.